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Abstract:

A mobile communication system according to the present invention
includes: a step A in which a radio base station eNB transmits an uplink
scheduling grant including CB-RNTI; and a step B in which when the uplink
scheduling grant has been received, according to a comparison result
obtained by comparing a predetermined threshold value with the amount of
uplink data remaining in the transmission buffer, the mobile station UE
determines whether a protocol data unit formed by the uplink data can be
transmitted using a shared uplink resource specified by the uplink
scheduling grant.

Claims:

1. A mobile communication method comprising: a step A in which a radio
base station transmits an uplink scheduling signal including
predetermined identification information which is not identification
information of a specific mobile station; and a step B in which when the
uplink scheduling signal has been received, according to a comparison
result obtained by comparing a predetermined threshold value with an
amount of uplink data remaining in a transmission buffer, a mobile
station determines whether a protocol data unit formed by the uplink data
can be transmitted using a shared uplink resource designated by the
uplink scheduling signal.

2. The mobile communication method according to claim 1, wherein in the
step B, the mobile station calculates the predetermined threshold value
based on at least one of a transmission format designated by the uplink
scheduling signal and a combination of a modulation scheme and a coding
scheme.

3. The mobile communication method according to claim 1, wherein in the
step B, only when the amount of the uplink data remaining in the
transmission buffer is equal to or more than the predetermined threshold
value, the mobile station determines that the protocol data unit formed
by the uplink data can be transmitted using the shared uplink resource.

4. The mobile communication method according to claim 1, wherein the
predetermined threshold value includes a first threshold value and a
second threshold value, and in the step B, only when the amount of the
uplink data remaining in the transmission buffer is equal to or more than
the first threshold value and is less than the second threshold value,
the mobile station determines that the protocol data unit formed by the
uplink data can be transmitted using the shared uplink resource.

5. The mobile communication method according to claim 1, wherein in step
B, only when an amount of padding in the protocol data unit formed by the
uplink data remaining in the transmission buffer is smaller than the
predetermined threshold value, the mobile station determines that the
protocol data unit can be transmitted using the shared uplink resource.

6. A mobile station comprising: a determination unit configured to, when
an uplink scheduling signal including predetermined identification
information that is not identification information of a specific mobile
station is received from a radio base station, determine whether a
protocol data unit formed by uplink data can be transmitted using a
shared uplink resource designated by the uplink scheduling signal,
according to a comparison result obtained by comparing a predetermined
threshold value with an amount of the uplink data remaining in a
transmission buffer.

7. The mobile station according to claim 6, wherein the determination
unit is configured to calculate the predetermined threshold value based
on at least one of a transmission format designated by the uplink
scheduling signal and a combination of a modulation scheme and a coding
scheme.

8. The mobile station according to claim 6, wherein only when the amount
of the uplink data remaining in the transmission buffer is equal to or
more than the predetermined threshold value, the determination unit is
configured to determine that the protocol data unit formed by the uplink
data can be transmitted using the shared uplink resource.

9. The mobile station according to claim 6, wherein the predetermined
threshold value includes a first threshold value and a second threshold
value, and only when the amount of the uplink data remaining in the
transmission buffer is equal to or more than the first threshold value
and is less than the second threshold value, the determination unit is
configured to determine that the protocol data unit formed by the uplink
data can be transmitted using the shared uplink resource.

10. The mobile station according to claim 6, wherein only when an amount
of padding in the protocol data unit formed by the uplink data remaining
in the transmission buffer is smaller than the predetermined threshold
value, the determination unit is configured to determine that the
protocol data unit can be transmitted using the shared uplink resource.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a mobile communication method and
a mobile station.

BACKGROUND ART

[0002] The Standards Determination Committee for LTE (Long Term

[0003] Evolution)-Advanced schemes has proposed adaptation of a
contention-based uplink transmission control method using "Contention
Based Grant" (see Non-Patent Document 1). A contention-based uplink
transmission control method using the "Contention Based Grant" will be
simply described below.

[0004] Firstly, in addition to an uplink scheduling grant transmitted
through PDCCH (Physical Downlink Control Channel) addressed to C-RNTI
(Cell-Radio Network Temporary Identity) of a mobile station UE, the
mobile station UE can monitor and receive an uplink scheduling grant
transmitted though the PDCCH addressed to CB-RNTI (Contention Based-Radio
Network Temporary Identity).

[0005] Secondly, when the mobile station UE has received an uplink
scheduling grant transmitted though PDCCH addressed to CB-RNTI, an uplink
data signal is transmitted through PUSCH (Physical Uplink Shared Channel)
using TF (Transmission Format), MCS (Modulation and Code Scheme), RB
(Resource Blocks) or the like that are designated by the uplink
scheduling grant.

[0006] The mobile station UE adds "MAC CE (Control Element)" including the
C-RNTI of the mobile station UE to the uplink data signal to enable
identification of by whom the uplink data signal has been transmitted.

[0007] As a result, application of the contention-based uplink
transmission control method using the "Contention Based Grant" is
expected to be capable of a reduction in transmission delay of the uplink
data signal by enabling omission of the L2 procedure of "transmission of
scheduling request by mobile station UE"→"transmission of uplink
scheduling grant by radio base station eNB", →"transmission of
buffer status report by mobile station UE", →"transmission of
uplink scheduling grant by radio base station eNB", →"transmission
of uplink data signal by mobile station UE".

[0008] Application of contention-based uplink transmission control method
using "Contention Based Grant" is expected to be capable of effective
application to uplink resources that are not used after normal scheduling
addressed to the C-RNTI.

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0009] However, the collision-type uplink transmission control method
using the "Contention Based Grant" which has currently been examined has
a problem in that a probability of the collision of the uplink data
signal may be increased or an interference amount of the uplink data
signal may be increased due to an increase in the number of mobile
stations UE which transmit the uplink data signal to the uplink
scheduling grant transmitted via the PDCCH addressed to the same CB-RNTI.

[0010] Furthermore, the collision-type uplink transmission control method
using the "Contention Based Grant" has another problem in that since it
is not possible to recognize by which mobile station UE at a particular
position the uplink data signal is to be transmitted, the radio base
station eNB selects TF or MCS based on quality for a mobile station UE
located at the end of the cell, and transmits only an uplink signal with
a small data amount, resulting in the occurrence of inefficiency.

[0011] Furthermore, the collision-type uplink transmission control method
using the "Contention Based Grant" has a problem in that when the uplink
signal is transmitted by the mobile station UE, in which a sufficient
amount of uplink data does not exist in a transmission buffer, with
respect to TF designated by the uplink scheduling grant transmitted via
the PDCCH addressed to the same CB-RNTI, most of PDUs (Protocol Data
Units) constituting the uplink data signal are filled with padding, so
that throughput may deteriorate.

[0012] Therefore, the present invention has been achieved in view of the
above-described problems, and an object thereof is to provide a mobile
communication method and a mobile station, by which it is possible to
solve the problems in the collision-type uplink transmission control
method using the "Contention Based Grant" as described above.

Means for Solving the Problem

[0013] A first characteristic of the present invention is summarized as a
mobile communication method comprising, a step A in which a radio base
station transmits an uplink scheduling signal including predetermined
identification information which is not identification information of a
specific mobile station, and a step B in which when the uplink scheduling
signal has been received, according to a comparison result obtained by
comparing a predetermined threshold value with an amount of uplink data
remaining in a transmission buffer, a mobile station determines whether a
protocol data unit formed by the uplink data can be transmitted using a
shared uplink resource designated by the uplink scheduling signal.

[0014] A second characteristic of the present invention is summarized as a
mobile station comprising a determination unit configured to, when an
uplink scheduling signal including predetermined identification
information that is not identification information of a specific mobile
station is received from a radio base station, determine whether a
protocol data unit formed by uplink data can be transmitted using a
shared uplink resource designated by the uplink scheduling signal,
according to a comparison result obtained by comparing a predetermined
threshold value with an amount of the uplink data remaining in a
transmission buffer.

Effect of the Invention

[0015] As described above, according to the present invention, it is
possible to provide a mobile communication method and a mobile station,
by which it is possible to solve the problems in the collision-type
uplink transmission control method using the "Contention Based Grant" as
described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [FIG. 1] FIG. 1 is an entire configuration diagram of a mobile
communication system according to a first embodiment of the present
invention.

[0017] [FIG. 2] FIG. 2 is a functional block diagram of a mobile station
according to the first embodiment of the present invention.

[0018] [FIG. 3] FIG. 3 is a sequence diagram illustrating the operation of
the mobile communication system according to the first embodiment of the
present invention.

[0019] [FIG. 4] FIG. 4 is a sequence diagram illustrating the operation of
the mobile communication system according to a first embodiment of the
present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

[0020] (Configuration of Mobile Communication System According to First
Embodiment of the Present Invention)

[0021] With reference to FIG. 1 and FIG. 2, the configuration of the
mobile communication system according to the first embodiment of the
present invention will be described.

[0022] The mobile communication system according to the present embodiment
is an LTE-Advanced mobile communication system that is configured to
apply a contention-based uplink transmission control method using
"Contention Based Grant" in relation to a mobile station UE that
maintains an uplink synchronous state.

[0023] As illustrated in FIG. 1, the mobile communication system according
to the present embodiment is configured so that a mobile station UE
transmits an uplink data signal through PUSCH to a radio base station
eNB, and transmits an uplink control signal through PUCCH (Physical
Uplink Control Channel).

[0024] Meanwhile, in the mobile communication system according to the
present embodiment, the radio base station eNB is configured to transmit
a downlink data signal to the mobile station UE through

[0025] PDSCH (Physical Downlink Shared Channel) and transmit a downlink
control signal to the mobile station UE through PDCCH.

[0026] As illustrated in FIG. 2, the mobile station UE includes a
reception unit 11, a transmission buffer 12, a determination unit 13, and
a transmission unit 14.

[0027] The reception unit 11 is configured to receive broadcast
information, an RRC message, a downlink control signal and the like,
which are transmitted from the radio base station eNB.

[0028] For example, the reception unit 11 is configured to receive, as a
downlink control signal, an uplink scheduling grant transmitted via the
PDCCH addressed to the C-RNTI of the mobile station UE, in other words,
an uplink scheduling grant (an uplink scheduling signal) including the
C-RNTI of the mobile station UE via the PDCCH.

[0029] Furthermore, the reception unit 11 is configured to receive, as the
downlink control signal, an uplink scheduling grant transmitted via the
PDCCH addressed to CB-RNTI, in other words, an uplink scheduling grant
(uplink scheduling signal) including the CB-RNTI.

[0030] The CB-RNTI is predetermined identification information that is not
CR-NTI for a specific mobile station UE, and may be designated by
broadcast information by the radio base station eNB, or may be designated
by separate signaling by the radio base station eNB (for example, an RRC
message).

[0031] The transmission buffer 12 is a buffer that houses uplink data to
be transmitted via the PUSCH.

[0032] The determination unit 13 is configured to determine whether it is
possible to transmit a protocol data unit formed by uplink data using a
shared uplink resource designated by the uplink scheduling grant
including the CB-RNTI according to a comparison result obtained by
comparing the amount of the uplink data remaining in the transmission
buffer with a predetermined threshold value.

[0033] Here, since the uplink scheduling grant including the CB-RNTI
designates the uplink resource that can be used by a plurality of mobile
stations UE, an uplink resource designated by the uplink scheduling grant
will be referred to as a "shared uplink resource" in the present
specification.

[0034] Meanwhile, since the uplink scheduling grant including the C-RNTI
of a specific mobile station UE designates an uplink resource that can be
used only by the mobile station UE, an uplink resource designated by the
uplink scheduling grant will be referred to an "individual uplink
resource" in the present specification.

[0035] In addition, the determination unit 13 may be configured to
calculate a predetermined threshold value based on at least one of TF
(Transmission Format) and MCS (Modulation and Code Scheme) designated by
the uplink scheduling grant including the CB-RNTI or may be configured to
use a predetermined threshold value designated by the radio base station
eNB.

[0036] Here, parameters necessary for calculating the above-described
predetermined threshold value may be set in advance by "RRC
Reconfiguration (an RRC message)" and the like.

[0037] For example, only when the amount of uplink data remaining in the
transmission buffer is equal to or more than the predetermined threshold
value, the determination unit 13 may be configured to determine that the
protocol data unit formed by the uplink data can be transmitted using the
shared uplink resource designated by the uplink scheduling grant
including the CB-RNTI.

[0038] In addition, the predetermined threshold value may include a
threshold value #1 (a first threshold value) and a threshold #2 (a second
threshold value). In this case, for example, only when the amount of
uplink data remaining in the transmission buffer is equal to or more than
the threshold value #1 and is less than the threshold value #2, the
determination unit 13 may be configured to determine that the protocol
data unit formed by the uplink data can be transmitted using the shared
uplink resource designated by the uplink scheduling grant including the
CB-RNTI.

[0039] Moreover, only when the amount of padding in the protocol data unit
formed by the uplink data remaining in the transmission buffer is smaller
than the predetermined threshold value, the determination unit 13 may be
configured to determine that the protocol data unit can be transmitted
using the shared uplink resource designated by the uplink scheduling
grant including the CB-RNTI.

[0040] The transmission unit 14 is configured to transmit the uplink data
signal, the uplink control signal, and the like to the radio base station
eNB.

[0041] For example, the transmission unit 14 is configured to transmit the
uplink data signal including the protocol data units determined to be
transmittable by the determination unit 13 to the radio base station eNB
via the PUSCH using the shared uplink resource designated by the uplink
scheduling grant including the CB-RNTI.

[0042] (Operation of Mobile Communication System According to First
Embodiment of Present Invention)

[0043] With reference to FIG. 3 and FIG. 4, the operation of the mobile
communication system according to the first embodiment of the present
invention will be described.

[0044] Firstly, as illustrated in FIG. 3, in step S1001, the radio base
station eNB transmits the "RRC Reconfiguration (RRC message)" to the
mobile station UE, wherein the "RRC Reconfiguration" indicates the
CB-RNTI receivable in the mobile station UE.

[0045] In addition, the radio base station eNB may designate parameters,
which are necessary for calculating the above-described predetermined
threshold value, by the "RRC Reconfiguration", to the mobile station UE.

[0046] In step S1002, the mobile station UE transmits "RRC Reconfiguration
Complete" to the radio base station eNB.

[0047] In step S1010, the radio base station eNB transmits an uplink
scheduling grant including CB-RNTI, TF, MCS, and the like via the PDCCH.

[0048] In step S1011, the mobile station UE calculates a predetermined
threshold value based on the TF, the MCS, and the like which are included
in the received uplink scheduling grant. Then, according to a comparison
result obtained by comparing the calculated predetermined threshold value
with the amount of uplink data remaining in the transmission buffer, the
mobile station UE determines whether a protocol data unit formed by the
uplink data can be transmitted using a shared uplink resource designated
by the uplink scheduling grant.

[0049] When the determination result is "OK", the mobile station UE
transmits an uplink data signal including a protocol data units, which
formed by the above-described uplink data, to the radio base station eNB
by using the shared uplink resource designated by the uplink scheduling
grant via the PUSCH in step S1012.

[0050] Secondly, as illustrated in FIG. 4, in step S2001, the radio base
station eNB transmits "RRC Reconfiguration (an RRC message)" to the
mobile station UE, wherein the "RRC Reconfiguration" indicates CB-RNTI
receivable by the mobile station UE.

[0051] In addition, the radio base station eNB may designate parameters #1
and #2, which are necessary for calculating threshold values #1 and #2,
by the "RRC Reconfiguration", to the mobile station UE.

[0052] In step S2002, the mobile station UE transmits "RRC Reconfiguration
Complete" to the radio base station eNB.

[0053] In step S2003, the radio base station eNB transmits an uplink
scheduling grant including CB-RNTI, TF #1, MCS #1, and the like, via the
PDCCH.

[0054] In step S2004, the mobile station UE calculates the threshold
values #1 and #2 based on the TF #1, the MCS #1, the parameters #1 and
#2, and the like which are included in the received uplink scheduling
grant. In step S2005, according to a comparison result obtained by
comparing the calculated threshold values #1 and #2 with the amount of
uplink data remaining in the transmission buffer, the mobile station UE
determines whether a protocol data unit formed by the uplink data can be
transmitted using the shared uplink resource designated by the uplink
scheduling grant.

[0055] When the determination result is "NG", the mobile station UE does
not transmit the uplink data signal, which includes the protocol data
units formed by the above-described uplink data, to the radio base
station eNB by using the shared uplink resource designated by the uplink
scheduling grant via the PUSCH.

[0056] Then, in step S2006, the radio base station eNB transmits again an
uplink scheduling grant including CB-RNTI, TF #2, MCS #2, and the like,
via the PDCCH.

[0057] In step S2007, the mobile station UE calculates the threshold
values #1 and #2 based on the TF #2, the MCS #2, the parameters #1 and
#2, and the like included in the received uplink scheduling grant. In
step S2008, according to a comparison result obtained by comparing the
calculated threshold values #1 and #2 with the amount of uplink data
remaining in the transmission buffer, the mobile station UE determines
whether a protocol data unit formed by the uplink data can be transmitted
using the shared uplink resource designated by the uplink scheduling
grant.

[0058] When the determination result is "OK", the mobile station UE
transmits the uplink data signal, which includes the protocol data units
formed by the above-described uplink data, to the radio base station eNB
by using the shared uplink resource designated by the uplink scheduling
grant via the PUSCH in step S2009.

[0059] (Operation and effect of mobile communication system according to
first embodiment of present invention)

[0060] In the mobile communication system according to the first
embodiment of the present invention, it is possible to omit useless
padding in the protocol data unit constituting the uplink data signal
transmitted using a shared resource, to reduce a probability of the
collision of the uplink data signals, and to improve a transmission
efficiency in the shared resource.

[0061] Furthermore, in the mobile communication system according to the
first embodiment of the present invention, the radio base station eNB
controls the predetermined threshold value to change assumed quality such
as quality for the mobile station UE located at the end of a cell,
quality for the mobile station UE located in the center of the cell, or
quality for the mobile station UE located in the vicinity of the radio
base station eNB, thereby controlling the number of resource blocks
assigned by the uplink scheduling grant including the CB-RNTI, the TF,
the MCS, and the like.

[0062] The characteristics of the present embodiment as described above
may be expressed as follows.

[0063] A first characteristic of the present embodiment is summarized in
that a mobile communication method includes: a step A in which the radio
base station eNB transmits an uplink scheduling grant (an uplink
scheduling signal) including CB-RNTI (predetermined identification
information which is not identification information of a specific mobile
station); and a step B in which when the uplink scheduling signal has
been received, according to a comparison result obtained by comparing a
predetermined threshold value with the amount of uplink data remaining in
the transmission buffer, the mobile station UE determines whether a
protocol data unit formed by the uplink data can be transmitted using a
shared uplink resource designated by the uplink scheduling grant.

[0064] In the first characteristic of the present embodiment, in the step
B, the mobile station UE may calculate the predetermined threshold value
based on at least one of a transmission format designated by the uplink
scheduling grant and a combination of a modulation scheme and a coding
scheme.

[0065] In the first characteristic of the present embodiment, in the step
B, only when the amount of the uplink data remaining in the transmission
buffer is equal to or more than the predetermined threshold value, the
mobile station UE may determine that the protocol data unit formed by the
uplink data can be transmitted using the shared uplink resource.

[0066] In the first characteristic of the present embodiment, the
predetermined threshold value includes a threshold value #1 (a first
threshold value) and a threshold value #2 (a second threshold value).

[0067] In the step B, only when the amount of the uplink data remaining in
the transmission buffer is equal to or more than the threshold value #1
and is less than the threshold value #2, the mobile station UE may
determine that the protocol data unit formed by the uplink data can be
transmitted using the shared uplink resource.

[0068] In the first characteristic of the present embodiment, in the step
B, only when the amount of padding in the protocol data unit formed by
the uplink data remaining in the transmission buffer is smaller than the
predetermined threshold value, the mobile station UE may determine that
the protocol data unit can be transmitted using the shared uplink
resource.

[0069] A second characteristic of the present embodiment is summarized in
that the mobile station UE includes the determination unit 13 configured
to, when an uplink scheduling grant including CB-RNTI is received from
the radio base station eNB, determine whether a protocol data unit formed
by uplink data can be transmitted using a shared uplink resource
designated by the uplink scheduling grant, according to a comparison
result obtained by comparing a predetermined threshold value with the
amount of the uplink data remaining in the transmission buffer.

[0070] In the second characteristic of the present embodiment, the
determination unit 13 may be configured to calculate the predetermined
threshold value based on at least one of a transmission format designated
by the uplink scheduling grant and a combination of a modulation scheme
and a coding scheme.

[0071] In the second characteristic of the present embodiment, only when
the amount of the uplink data remaining in the transmission buffer is
equal to or more than the predetermined threshold value, the
determination unit 13 may be configured to determine that the protocol
data unit formed by the uplink data can be transmitted using the shared
uplink resource.

[0072] In the second characteristic of the present embodiment, the
predetermined threshold value includes a threshold value #1 and a
threshold value #2. Only when the amount of the uplink data remaining in
the transmission buffer is equal to or more than the threshold value #1
and is less than the threshold value #2, the determination unit 13 may be
configured to determine that the protocol data unit formed by the uplink
data can be transmitted using the shared uplink resource.

[0073] In the second characteristic of the present embodiment, only when
the amount of padding in the protocol data unit formed by the uplink data
remaining in the transmission buffer is smaller than the predetermined
threshold value, the determination unit 13 may be configured to determine
that the protocol data unit can be transmitted using the shared uplink
resource.

[0074] It is noted that the operation of the above-described the radio
base station eNB or the mobile station UE may be implemented by a
hardware, may also be implemented by a software module executed by a
processor, and may further be implemented by the combination of the both.

[0075] The software module may be arranged in a storage medium of an
arbitrary format such as RAM(Random Access Memory), a flash memory, ROM
(Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM
(Electronically Erasable and Programmable ROM), a register, a hard disk,
a removable disk, and CD-ROM.

[0076] The storage medium is connected to the processor so that the
processor can write and read information into and from the storage
medium. Such a storage medium may also be accumulated in the processor.
The storage medium and processor may be arranged in ASIC. Such the ASIC
may be arranged in the radio base station eNB or the mobile station UE.
Further, such a storage medium or a processor may be arranged, as a
discrete component, in the radio base station eNB or the mobile station
UE.

[0077] Thus, the present invention has been explained in detail by using
the above-described embodiments; however, it is obvious that for persons
skilled in the art, the present invention is not limited to the
embodiments explained herein. The present invention can be implemented as
a corrected and modified mode without departing from the gist and the
scope of the present invention defined by the claims. Therefore, the
description of the specification is intended for explaining the example
only and does not impose any limited meaning to the present invention.